What have I missed? (or did wrong?)

win · Oct 29, 2014

Think I'm getting ready to abandon the current 5.0 in my Ranger and build another -- have been going nuts trying to track down a seemingly RPM related miss and sub-standard fuel economy.

It's a 1996 5.0 in my 02 Ranger.

Engine was refreshed with new rings/bearings/valve springs etc -- internals all mic'd to near new spec.

Diff is an Expo 8.8 with 3.27:1 gears, has me at about 2000 rpm at 65 mph.

No check engine light/fault codes
130/135 psi compression cold/dry across all 8 cylinders
Long and short term fuel trims hover around 0%
Miss seems at it's worst between 1500 and 1700 RPM
Idles with 23" to 24" of vacuum
Fuel pressure runs 29 psi with vacuum applied, 38 psi without vacuum -- tried an adjustable FPR setting the pressures at 35 and 45 psi (LTFT's moved to -7%)
0 PSI of exhaust pressure at the front O2 sensors at 50 mph.
Two different sets of ignition wires
Two different sets of spark plugs
Two different sets of ignition coils
Two different ECU's
Two different cam position sensors
Two different crank position sensors
Two different sets of fuel injectors.
Two different air filters
Cam timing has been verified -- cam position sensor timed while the timing cover was off the engine.
Tried different O2 sensors and swapping them side for side.
Engine temp sensor and coolant temp sensor appear to agree with the thermostat.
PCM seems to correctly toggle between open and closed loop.
TPS shows very smooth readings from fully closed to fully open

Think only the MAF, IAC and TPS are original

So, two questions: Does anyone have any ideas what I might have missed?

And, would a GT40P based '97 5.0 still support the "through the intake" EGR of my '96 manifolds? I've found a great deal on a reasonable miles external EGR 5.0.

win · Nov 1, 2014

Before absolutely throwing in the towel, though I'd try a few more things:

New MAF and different TPS, no change.

Using Forscan, have poked around the PCM, only issues it picks up that neither Torque nor my Actron 9180 were a pair of codes, P1137 and P1157 -- both rear O2 sensors reading lean.

Hmmm, well, what the heck, a pair of new sensors is a heck of a lot less work and money than swapping out the engine.

Gotta make an order from Rockauto for the wife's ride anyway so will try that.

win · Nov 5, 2014

As so it begins anew!

85K miles, $400 out the door complete except for the left exhaust manifold that I won't use anyway.

The "plan" is a quick clean up, strip to a long block, leave the heads on check up and install -- NO idea what I'll do if the problem survives this!

With this, I'll have a complete 2nd pre PATS EFI system with FEAD and manifolds. Hmmm, the possibilities are endless!

RonD · Nov 5, 2014

Rear O2 sensors are just to check Cat convert function so wouldn't cause a miss, but to get the lean code it would mean the front O2 sensors were rich, but at 0 on STFT/LTFT that wouldn't make sense.

But the substandard MPG would mean engine is running rich

Stock Exhaust manifolds should be running around -3psi in the mid-range RPM(power) band, O2 sensor is on the collector not manifold.
Because of the negative pressure an exhaust manifold leak will pull air in, this gives a false Lean reading on the O2 sensor(on that bank only), computer adds more fuel than needed so MPG goes down, but this should show up on LTFT as a + number

Intermittent misfire is lack spark at the right time, or lack of correct air/fuel mix.
It could also be a floating valve seat or valve train issue causing intermittent low compression but it is a long shot, not no shot, just long shot.

I assume you have pulled the spark plugs a few times and there is no way to ID if it is just one cylinder that has the intermittent problem or if it is a random cylinder miss.

Out side of being stuck Open a non-functioning EGR system would allow engine to ping under load but wouldn't cause a miss.
EGR is just use to cool cylinders down when they heat up under load.

TPS sensor can cause issues in specific RPM range.
If you put on a new one you do need to adjust it for between .7-.9volts with throttle closed

win · Nov 5, 2014

RonD, you've given a pretty solid recap of why I'm at such a loss on this. I get symptoms that simply don't agree with the data I can collect from the system.

Worse, at this point, other than the wiring harness, IAC and hard mechanicals, I've replaced or swapped out the entire ignition and EFI system, all without changing the symptoms.

The only ideas I've got left are all pretty implausible. Of course, there's that old adage about once you've eliminated all the plausible options, the remaining, no matter how implausible must be the answer.

1st is somehow I mucked up lapping the valves and I've got a very even "leak" across all 8 cylinders, so even the PCM never detects the miss/stutter in the engine but severe enough to rob the engine of a significant portion of it's efficiency.

2nd is I've got an alien cam in the engine and the PCM simply does not know how to run the engine correctly with the cam timing and profiles.

3rd is I've got a significant blockage in one of the Torque monster headers (or both of them)

I never tried a vacuum gauge when testing for clogged cats or a restriction in the exhaust. The lack of any popping noises at idle from escaping exhaust gasses did not get me thinking along those lines. Might give that test a try

While I'm doing the swap, I'll go over the TM's with a fine toothed comb and swapping the long block will remove a significant amount of the hard mechanicals. Swapping out the complete engine with an unmolested, single owner 85K mile example should eliminate anything internal.

Should the symptoms persist after the swap, I'd have to re-consider what I think of as implausible!

win · Dec 26, 2014

And it's Deja Vu!

Almost like deja vu all over again!

Pulled the 5.0 out of the Ranger this afternoon. Whew!

Got the engine and trans separated, will start transferring the few bits I'll keep from the 1st onto the 2nd in the morning.

Ford came through with a pair if 4R70W accumulator springs so I'll pop off the pan on gearbox and get that done before the two big bits go back together and into the engine bay.

Don't know what I'm looking forward to the most: Getting the Ranger to run right or finding out what the heck is wrong with the 1st 5.0. Yea, getting the pep that has slowly faded back along with reasonable fuel economy will be great but man oh man do I HATE not knowing what's wrong.

Really does not matter, if all goes well, I'll get both answers and the 5.0 that runs right!

win · Dec 27, 2014

Got nearly everything transferred from the 1st 5.0 onto the 2nd.

Trying to work out a better oil pan solution. I'd originally used a FRP dual sump pan but it's too deep at the rack and pinion and too wide at the left down pipe.

The OEM Explorer ones are shallower at the front, have a huge notch out in them for the down pipe but don't clear the front cross member at the rear of the cross member/front of the sump.

So, I've re-worked the lower front edge of the sump back to almost the drain plug. With the two sumps side by side, I've got nearly the same profile on the Expo sump now as the dual so I've hopes that I've gained the clearance needed for the cross member.

One "interesting" thing I found in the dual sump -- there was a heavy smear of metallic mud just behind the front drain plug. Bottom of the rear sump was clean. Thinking that my suspicion of a failing lifter or wiped cam lob (or two) is starting to carry some more weight. Gotta get the Ranger back on the road before I dig deeper but still, I WILL find out what's wrong in there!

dSINtia · Dec 27, 2014

Good luck bro. Interested to know what you come to.

win · Jan 2, 2015

Well, the replacement is in and running -- always nice when it starts on the 1st try. Should have it fully back on the road tomorrow.

Do have an exhaust leak I need to track down and my 1st temp sensor solution is misbehaving. At 170°f, the dash gauge pegs and the "check gage" light comes on. Think I need to add a ground for the sensor.

As expected, I did find a broken spring in the 1st/2nd accumulator -- no idea what color that spring is that was mated to the yellow, I put in a std pair of white/pink springs. 1st to 2nd shifts are significantly improved.

Took the time to really add some clearance to the oil pan. Final solution uses the dual sump oil pick up and the modified Explorer 5.0 steel pan. The pan gave me fits brazing it, the metal was so stressed from the initial shaping that I was getting leaks inches away from where I'd cut and spliced the darn thing. Given the troubles and how thin the steel was, I opted NOT to do any cleanup of the brazing. Might not be pretty but it fits well and gives the clearance I need both front and back.

Do need to get a pic of the modded 3.0 fan shroud I installed -- a much better fit overall than the 5.0 Explorer one.

win · Jan 3, 2015

Pic of the 3.0 fan shroud, trimmed 7/8" off the top and bottom leading edges to account for the deeper radiator core and 1/2" off the bottom of the right side (passenger's) tab that slots into the radiator.

Fits quite well, should do until I build and install a dual electric fan solution.

What have I missed? (or did wrong?)

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